BJA
Correspondence
Declaration of interest None declared. B. Gibbison* S. L. Lightman Bristol, UK *E-mail: [email protected] 1 Aslam R, Ducrocq N, Thivilier C, et al. Critical illness-related corticosteroid insufficiency in cardiogenic shock. Br J Anaesth 2013; 111: 512– 3 2 Gibbison B, Angelini GD, Lightman SL. Dynamic output and control of the hypothalamic– pituitary –adrenal axis in critical illness and major surgery. Br J Anaesth 2013; 111: 347–60
3 Longmore M, Wilkinson IB, Rajagopalan S. Oxford Handbook of Clinical Medicine, 6th Edn. Oxford: Oxford University Press, 2004 4 Marik PE, Varon J. Requirement of perioperative stress doses of corticosteroids: a systematic review of the literature. Arch Surg 2008; 143: 1222–6 5 Zaghiyan K, Melmed G, Murrell Z, Fleshner P. Are high-dose perioperative steroids necessary in patients undergoing colorectal surgery treated with steroid therapy within the past 12 months? Am Surg 2011; 77: 1295– 9 6 Zaghiyan K, Melmed G, Murrell Z, Fleshner P. Safety and feasibility of using low-dose perioperative intravenous steroids in inflammatory bowel disease patients undergoing major colorectal surgery: a pilot study. Surgery 2012; 152: 158– 63 7 Henley DE, Leendertz JA, Russell GM, et al. Development of an automated blood sampling system for use in humans. J Med Eng Technol 2009; 33: 199– 208 8 Gibbison B, Sheikh A, McShane P, Haddow C, Soar J. Anaphylaxis admissions to UK critical care units between 2005 and 2009. Anaesthesia 2012; 67: 833– 9 9 The Society for Cardiovascular Surgery. The Blue Book Online. Available from http://bluebook.scts.org/#CrudeMortality (accessed 2 September 2013) 10 Padkin A, Goldfrad C, Brady AR, Young D, Black N, Rowan K. Epidemiology of severe sepsis occurring in the first 24 hrs in intensive care units in England, Wales, and Northern Ireland. Crit Care Med 2003; 31: 2332– 8 11 Boonen E, Vervenne H, Meersseman P, et al. Reduced cortisol metabolism during critical illness. N Engl J Med 2013; 368: 1477– 88
doi:10.1093/bja/aeu065
It is 3 a.m. . . . do you know where your catheter tip is? Editor—Marhofer and colleagues1 have recently reported a high rate of perineural catheter dislocation (25% for femoral catheters and 5% for interscalene catheters). While their results should be confirmed in a clinical setting, the reported data are consistent with previous literature on secondary block failure.2 – 4 The finding that only 75% of femoral catheters placed under ultrasound guidance would be expected to provide effective analgesia at 6 h should raise substantial concerns, especially since they were performed in fit volunteers by expert practitioners. Actual patients may have a higher BMI and much longer indwelling time (typically 48 –72 h or longer), both of which are likely to predispose to higher dislodgement rates. Since many institutions rely on femoral nerve catheters as the primary analgesic method for patients after total knee replacement, the data by Marhofer and colleagues1 suggest that a substantial proportion of these patients may not receive the presumed analgesic benefit from their catheters. Of note, no standards with regard to techniques of catheter insertion, their pharmacological management and securing to prevent dislocation have been established despite two decades of widespread use.5 There is no doubt that the technique used by this expert group is just one of many, and while the relative merits of various technical aspects could (and probably will) be debated, this is besides the more pressing point: if efforts to reduce secondary failure
757
Downloaded from http://bja.oxfordjournals.org/ at Universitaets- und Landesbibliothek Duesseldorf on March 25, 2014
and critical illness.4 – 6 Secondly, cortisol levels are rapidly dynamic and pulsatile by over 21 mg dl21 (600 nmol litre21) within an hour.7 Therefore, a point measurement of 8 mg dl21 alone does not tell one anything about what the cortisol level might be 1 h later. The measurement in this patient may simply be at the nadir of a pulse. There are numerous other gaps in our understanding of the physiology of the HPA axis during critical illness that makes diagnosis of corticosteroid insufficiency around this time almost impossible. No test has been shown to accurately identify cortisol insufficiency, primarily as there is no accurate model for what constitutes ‘normality’. The inflammatory response is dynamic and it is likely that the glucocorticoid requirements vary throughout a patient’s illness. Glucocorticoid needs on day 1 may not be the same as day 3 or day 5, and indeed, this is one of the major gaps in our knowledge. The question of whether glucocorticoids in supra-physiological doses merely function as a non-catecholamine vasopressor is to be answered separately from trying to diagnose those with CIRCI, although much of the literature confuses these. There are too many confounders in this case report to state that the patient’s poor haemodynamic state was as a result of glucocorticoid deficiency. Starting glucocorticoids on the third day post-insult may simply correlate with the resolution of the inflammatory response. Sterile, point insults causing a systemic inflammatory response appear to reach their peak level at around day 3 and then improve. This can be well seen after cardiac surgery, where the peak CRP and white cell count and the nadir in renal function all occur on or around day 3. The inflammation of a sterile systemic insult should not be confused with the ongoing inflammation of sepsis as can be seen from their vastly different outcomes. Point, sterile insults such as anaphylaxis8 and cardiac surgery9 have critical care survival rates of around 95%, whereas all-cause sepsis on UK intensive care units has a survival rate of around 60%.10 The bottom line is that attempts to identify, diagnose, and treat CIRCI will fail without high-quality studies of HPA axis pathophysiology and fortunately, the recent year has begun to see a move towards this.11 Until, we truly understand the nature and mechanisms of HPA axis function in critical illness, we are unlikely to be able to design tools to improve it.
BJA
Correspondence
are not successful, we may have to critically examine the expense and effort involved in using perineural catheters. Alternatively, perhaps it is time to re-focus our efforts to other means of delivering long-acting analgesia with nerve blocks, rather than continuing to deliberate on technical and equipment considerations. If current studies on the use of sustained-release local anaesthetics (e.g. liposomal bupivacaine) for nerve blocks yield positive results, a precise, ultrasound-guided single injection of such agents may be the future.6 7
Declaration of interest
M. Levine* M. Latmore C. Vandepitte J. Gadsden A. Hadzic New York, USA *E-mail: [email protected] 1 Marhofer D, Marhofer P, Triffterer L, Leonhardt M, Weber M, Zeitlinger M. Dislocation rates of perineural catheters: a volunteer study. Br J Anaesth 2013; 111: 800– 6 2 Ganapathy S, Wasserman RA, Watson JT, et al. Modified continuous femoral three-in-one block for postoperative pain after total knee arthroplasty. Anesth Analg 1999; 89: 1197– 202 3 Ilfeld BM, Morey TE, Wright TW, Chidgey LK, Enneking FK. Continuous interscalene brachial plexus block for postoperative pain control at home: a randomized, double-blinded, placebo-controlled study. Anesth Analg 2003; 96: 1089–95 4 Grant SA, Nielsen KC, Greengrass RA, Steele SM, Klein SM. Continuous peripheral nerve block for ambulatory surgery. Reg Anesth Pain Med 2001; 26: 209–14 5 Ilfeld BM. Continuous peripheral nerve blocks: a review of the published evidence. Anesth Analg 2011; 113: 904– 25 6 Hu D, Onel E, Singla N, Kramer WG, Hadzic A. Pharmacokinetic profile of liposome bupivacaine injection following a single administration at the surgical site. Clin Drug Investig 2013; 33: 109 – 15 7 Ohri R, Blaskovich P, Wang JC-F, et al. Prolonged nerve block by microencapsulated bupivacaine prevents acute postoperative pain in rats. Reg Anesth Pain Med 2012; 37: 607– 15
doi:10.1093/bja/aeu069
Factors affecting perineural catheter dislocation rates Editor—We read with interest the article by Marhofer and colleagues1 investigating dislocation rates of perineural catheters (PNCs) in a volunteer study. As described, PNCs are often positioned in clinical practice to facilitate perioperative
758
Declaration of interest None declared. J. Francis* C. Egeler Swansea, UK *E-mail: [email protected] 1 Marhofer D, Marhofer P, Triffterer L, Weber M, Zeitlinger M. Dislocation rates of perineural catheters: a volunteer study. Br J Anaesth 2013; 111: 800– 6 2 Wang A-Z, Gu LL, Zhou Q-H, Ni W-Z, Jiang W. Ultrasound-guided continuous femoral nerve block for analgesia after total knee arthroplasty: catheter perpendicular to the nerve versus catheter parallel to the nerve. Reg Anesth Pain Med 2010; 35: 127– 31
doi:10.1093/bja/aeu064
Downloaded from http://bja.oxfordjournals.org/ at Universitaets- und Landesbibliothek Duesseldorf on March 25, 2014
A.H. has consulted and advised for Skypharma, GE, Sonosite, Codman & Shrutleff, Inc. (Johnson and Johnson), Cadence, Pacira, Baxter, and BBraun Medical. His recent industrysponsored research include Glaxo Smith-Kline Industries, Pacira, Baxter. A.H. is an equity holder at Macosta Medical USA.
anaesthesia and analgesia and thus, studies into their efficacy are often designed to assess perioperative pain. We agree that PNC dislocation is an important, yet poorly investigated, reason for failure of PNC anaesthesia or analgesia. We are however disappointed to find that, in our opinion, important information was omitted in the methodology of this otherwise welldesigned study. The technique described for insertion of the PNCs is an out-of-plane technique aiming to achieve passage under the fascia covering nerve structures as the needle tip entered the US beam. Catheters were advanced 3 cm beyond the tip of the needle and then retracted until appropriate spread of LA was seen around the nerve. The authors do not provide detail as to how far the catheter was in fact under the fascia in each case. We would be interested to see whether in the dislocated cases, the actual catheter length under the fascia was shorter than in the cases where dislocation did not occur. We would hypothesize that a catheter placed parallel to the femoral nerve with ,2–3 cm under the fascia iliaca is likely to dislodge with full hip flexion, being pulled out of the fascial plane to lie superficial to the fascia as the authors describe. We would further suggest that a catheter inserted perpendicular to the nerve would be less likely to be dislodged with exercise because less pull is being exerted on the catheter itself. In 2010, Wang and colleagues2 showed that catheters positioned parallel to the nerve have a higher insertion failure rate than those positioned perpendicular to the nerve; interestingly, they also showed significantly quicker insertion times for perpendicular catheters. The relatively low rate of dislocation reported for interscalene catheters may be because shoulder movement itself has less direct anatomical influence on neck structures; if subjects had been instructed to perform lateral neck flexion, thus exerting a direct pull on the catheter, the dislocation rate may well have been higher. Again we hypothesize that with an in-plane technique at the level of the supraclavicular trunks, positioning a catheter from posterior to the upper trunk to lie under the investing fascia may help to prevent dislocation. This topic would make for further interesting studies and we thank the authors for undertaking this novel work.
Correspondence
Declaration of interest None declared. B. Gibbison* S. L. Lightman Bristol, UK *E-mail: [email protected] 1 Aslam R, Ducrocq N, Thivilier C, et al. Critical illness-related corticosteroid insufficiency in cardiogenic shock. Br J Anaesth 2013; 111: 512– 3 2 Gibbison B, Angelini GD, Lightman SL. Dynamic output and control of the hypothalamic– pituitary –adrenal axis in critical illness and major surgery. Br J Anaesth 2013; 111: 347–60
3 Longmore M, Wilkinson IB, Rajagopalan S. Oxford Handbook of Clinical Medicine, 6th Edn. Oxford: Oxford University Press, 2004 4 Marik PE, Varon J. Requirement of perioperative stress doses of corticosteroids: a systematic review of the literature. Arch Surg 2008; 143: 1222–6 5 Zaghiyan K, Melmed G, Murrell Z, Fleshner P. Are high-dose perioperative steroids necessary in patients undergoing colorectal surgery treated with steroid therapy within the past 12 months? Am Surg 2011; 77: 1295– 9 6 Zaghiyan K, Melmed G, Murrell Z, Fleshner P. Safety and feasibility of using low-dose perioperative intravenous steroids in inflammatory bowel disease patients undergoing major colorectal surgery: a pilot study. Surgery 2012; 152: 158– 63 7 Henley DE, Leendertz JA, Russell GM, et al. Development of an automated blood sampling system for use in humans. J Med Eng Technol 2009; 33: 199– 208 8 Gibbison B, Sheikh A, McShane P, Haddow C, Soar J. Anaphylaxis admissions to UK critical care units between 2005 and 2009. Anaesthesia 2012; 67: 833– 9 9 The Society for Cardiovascular Surgery. The Blue Book Online. Available from http://bluebook.scts.org/#CrudeMortality (accessed 2 September 2013) 10 Padkin A, Goldfrad C, Brady AR, Young D, Black N, Rowan K. Epidemiology of severe sepsis occurring in the first 24 hrs in intensive care units in England, Wales, and Northern Ireland. Crit Care Med 2003; 31: 2332– 8 11 Boonen E, Vervenne H, Meersseman P, et al. Reduced cortisol metabolism during critical illness. N Engl J Med 2013; 368: 1477– 88
doi:10.1093/bja/aeu065
It is 3 a.m. . . . do you know where your catheter tip is? Editor—Marhofer and colleagues1 have recently reported a high rate of perineural catheter dislocation (25% for femoral catheters and 5% for interscalene catheters). While their results should be confirmed in a clinical setting, the reported data are consistent with previous literature on secondary block failure.2 – 4 The finding that only 75% of femoral catheters placed under ultrasound guidance would be expected to provide effective analgesia at 6 h should raise substantial concerns, especially since they were performed in fit volunteers by expert practitioners. Actual patients may have a higher BMI and much longer indwelling time (typically 48 –72 h or longer), both of which are likely to predispose to higher dislodgement rates. Since many institutions rely on femoral nerve catheters as the primary analgesic method for patients after total knee replacement, the data by Marhofer and colleagues1 suggest that a substantial proportion of these patients may not receive the presumed analgesic benefit from their catheters. Of note, no standards with regard to techniques of catheter insertion, their pharmacological management and securing to prevent dislocation have been established despite two decades of widespread use.5 There is no doubt that the technique used by this expert group is just one of many, and while the relative merits of various technical aspects could (and probably will) be debated, this is besides the more pressing point: if efforts to reduce secondary failure
757
Downloaded from http://bja.oxfordjournals.org/ at Universitaets- und Landesbibliothek Duesseldorf on March 25, 2014
and critical illness.4 – 6 Secondly, cortisol levels are rapidly dynamic and pulsatile by over 21 mg dl21 (600 nmol litre21) within an hour.7 Therefore, a point measurement of 8 mg dl21 alone does not tell one anything about what the cortisol level might be 1 h later. The measurement in this patient may simply be at the nadir of a pulse. There are numerous other gaps in our understanding of the physiology of the HPA axis during critical illness that makes diagnosis of corticosteroid insufficiency around this time almost impossible. No test has been shown to accurately identify cortisol insufficiency, primarily as there is no accurate model for what constitutes ‘normality’. The inflammatory response is dynamic and it is likely that the glucocorticoid requirements vary throughout a patient’s illness. Glucocorticoid needs on day 1 may not be the same as day 3 or day 5, and indeed, this is one of the major gaps in our knowledge. The question of whether glucocorticoids in supra-physiological doses merely function as a non-catecholamine vasopressor is to be answered separately from trying to diagnose those with CIRCI, although much of the literature confuses these. There are too many confounders in this case report to state that the patient’s poor haemodynamic state was as a result of glucocorticoid deficiency. Starting glucocorticoids on the third day post-insult may simply correlate with the resolution of the inflammatory response. Sterile, point insults causing a systemic inflammatory response appear to reach their peak level at around day 3 and then improve. This can be well seen after cardiac surgery, where the peak CRP and white cell count and the nadir in renal function all occur on or around day 3. The inflammation of a sterile systemic insult should not be confused with the ongoing inflammation of sepsis as can be seen from their vastly different outcomes. Point, sterile insults such as anaphylaxis8 and cardiac surgery9 have critical care survival rates of around 95%, whereas all-cause sepsis on UK intensive care units has a survival rate of around 60%.10 The bottom line is that attempts to identify, diagnose, and treat CIRCI will fail without high-quality studies of HPA axis pathophysiology and fortunately, the recent year has begun to see a move towards this.11 Until, we truly understand the nature and mechanisms of HPA axis function in critical illness, we are unlikely to be able to design tools to improve it.
BJA
Correspondence
are not successful, we may have to critically examine the expense and effort involved in using perineural catheters. Alternatively, perhaps it is time to re-focus our efforts to other means of delivering long-acting analgesia with nerve blocks, rather than continuing to deliberate on technical and equipment considerations. If current studies on the use of sustained-release local anaesthetics (e.g. liposomal bupivacaine) for nerve blocks yield positive results, a precise, ultrasound-guided single injection of such agents may be the future.6 7
Declaration of interest
M. Levine* M. Latmore C. Vandepitte J. Gadsden A. Hadzic New York, USA *E-mail: [email protected] 1 Marhofer D, Marhofer P, Triffterer L, Leonhardt M, Weber M, Zeitlinger M. Dislocation rates of perineural catheters: a volunteer study. Br J Anaesth 2013; 111: 800– 6 2 Ganapathy S, Wasserman RA, Watson JT, et al. Modified continuous femoral three-in-one block for postoperative pain after total knee arthroplasty. Anesth Analg 1999; 89: 1197– 202 3 Ilfeld BM, Morey TE, Wright TW, Chidgey LK, Enneking FK. Continuous interscalene brachial plexus block for postoperative pain control at home: a randomized, double-blinded, placebo-controlled study. Anesth Analg 2003; 96: 1089–95 4 Grant SA, Nielsen KC, Greengrass RA, Steele SM, Klein SM. Continuous peripheral nerve block for ambulatory surgery. Reg Anesth Pain Med 2001; 26: 209–14 5 Ilfeld BM. Continuous peripheral nerve blocks: a review of the published evidence. Anesth Analg 2011; 113: 904– 25 6 Hu D, Onel E, Singla N, Kramer WG, Hadzic A. Pharmacokinetic profile of liposome bupivacaine injection following a single administration at the surgical site. Clin Drug Investig 2013; 33: 109 – 15 7 Ohri R, Blaskovich P, Wang JC-F, et al. Prolonged nerve block by microencapsulated bupivacaine prevents acute postoperative pain in rats. Reg Anesth Pain Med 2012; 37: 607– 15
doi:10.1093/bja/aeu069
Factors affecting perineural catheter dislocation rates Editor—We read with interest the article by Marhofer and colleagues1 investigating dislocation rates of perineural catheters (PNCs) in a volunteer study. As described, PNCs are often positioned in clinical practice to facilitate perioperative
758
Declaration of interest None declared. J. Francis* C. Egeler Swansea, UK *E-mail: [email protected] 1 Marhofer D, Marhofer P, Triffterer L, Weber M, Zeitlinger M. Dislocation rates of perineural catheters: a volunteer study. Br J Anaesth 2013; 111: 800– 6 2 Wang A-Z, Gu LL, Zhou Q-H, Ni W-Z, Jiang W. Ultrasound-guided continuous femoral nerve block for analgesia after total knee arthroplasty: catheter perpendicular to the nerve versus catheter parallel to the nerve. Reg Anesth Pain Med 2010; 35: 127– 31
doi:10.1093/bja/aeu064
Downloaded from http://bja.oxfordjournals.org/ at Universitaets- und Landesbibliothek Duesseldorf on March 25, 2014
A.H. has consulted and advised for Skypharma, GE, Sonosite, Codman & Shrutleff, Inc. (Johnson and Johnson), Cadence, Pacira, Baxter, and BBraun Medical. His recent industrysponsored research include Glaxo Smith-Kline Industries, Pacira, Baxter. A.H. is an equity holder at Macosta Medical USA.
anaesthesia and analgesia and thus, studies into their efficacy are often designed to assess perioperative pain. We agree that PNC dislocation is an important, yet poorly investigated, reason for failure of PNC anaesthesia or analgesia. We are however disappointed to find that, in our opinion, important information was omitted in the methodology of this otherwise welldesigned study. The technique described for insertion of the PNCs is an out-of-plane technique aiming to achieve passage under the fascia covering nerve structures as the needle tip entered the US beam. Catheters were advanced 3 cm beyond the tip of the needle and then retracted until appropriate spread of LA was seen around the nerve. The authors do not provide detail as to how far the catheter was in fact under the fascia in each case. We would be interested to see whether in the dislocated cases, the actual catheter length under the fascia was shorter than in the cases where dislocation did not occur. We would hypothesize that a catheter placed parallel to the femoral nerve with ,2–3 cm under the fascia iliaca is likely to dislodge with full hip flexion, being pulled out of the fascial plane to lie superficial to the fascia as the authors describe. We would further suggest that a catheter inserted perpendicular to the nerve would be less likely to be dislodged with exercise because less pull is being exerted on the catheter itself. In 2010, Wang and colleagues2 showed that catheters positioned parallel to the nerve have a higher insertion failure rate than those positioned perpendicular to the nerve; interestingly, they also showed significantly quicker insertion times for perpendicular catheters. The relatively low rate of dislocation reported for interscalene catheters may be because shoulder movement itself has less direct anatomical influence on neck structures; if subjects had been instructed to perform lateral neck flexion, thus exerting a direct pull on the catheter, the dislocation rate may well have been higher. Again we hypothesize that with an in-plane technique at the level of the supraclavicular trunks, positioning a catheter from posterior to the upper trunk to lie under the investing fascia may help to prevent dislocation. This topic would make for further interesting studies and we thank the authors for undertaking this novel work.
